1. Field of the Invention
The present invention relates to a driving apparatus and an image pickup apparatus using the driving apparatus, and more particularly to a driving apparatus that moves a movable body in a predetermined direction with respect to a fixed body using a driving force of an actuator such as an electromagnetic motor, or an ultrasonic motor, and an image pickup apparatus such as a digital camera equipped with an image shake correction mechanism for correcting image shake by using the driving apparatus.
2. Description of the Related Art
In recent years, image pickup apparatuses such as digital cameras which include an image shake correction mechanism are put into practical use and widely used. In such an image shake correction mechanism, image shake correction is performed using a driving apparatus that appropriately moves a movable body equipped with an image pickup device and the like in a predetermined direction at a predetermined timing with respect to a fixed body by means of a driving force of an actuator such as an electromagnetic motor, an ultrasonic motor, or the like.
As an image shake correction mechanism applied to a conventional image pickup apparatus, such a mechanism is known in which shake vibration in a pitch direction and shake vibration in a yaw direction of the image pickup apparatus are detected using shake detecting means such as an angular velocity sensor, and based on a detected shake signal, a part of photographing optical system or the image pickup device is moved independently in a horizontal direction and in a vertical direction within a plane perpendicular to an optical axis of the photographing optical system to cancel an image shake, thereby correcting the image shake of an optical image formed on an image pickup surface of the image pickup device.
Such an image shake correction mechanism includes a driving apparatus which moves optical elements (lenses) as a part of photographing optical system or the image pickup device in a horizontal direction and in a vertical direction within the plane perpendicular to the optical axis of the photographing optical system.
The driving apparatus is required to be capable of performing very precise driving (minute driving) so as to cause the image shake correction mechanism to follow image shake. When the image shake correction mechanism is driven by the driving apparatus, the driving apparatus is required to have a configuration and precision for accurately determining a position of a movable body, i.e., a position of an image pickup surface with respect to the photographing optical system. Furthermore, in order to drive the image shake correction mechanism by the driving apparatus, the driving apparatus is required to have a large amount of driving force to overcome the gravity of the movable body and obtain acceleration necessary for controlling the image shake correction mechanism. In addition, when the power is turned off, the driving apparatus is required to have a self-retaining property to retain the position of the movable body at a predetermined position. In addition to these conditions, it is needless to say that the image shake correction mechanism using the driving apparatus is preferably a size-reduced and inexpensive mechanism.
For example, Japanese Patent Application Laid-Open Publication No. 2008-172995 and the like propose various kinds of image shake correction mechanisms using conventional driving apparatuses.
A driving apparatus disclosed in the Japanese Patent Application Laid-Open Publication No. 2008-172995 includes a sliding body arranged in a movable body, a transducer which vibrates by contacting the sliding body and is retained in a fixed body, and a plurality of rolling bodies arranged between the sliding body and the fixed body.
Specifically, the rolling bodies (balls) are arranged between a linear V-groove formed on a fixed body (frame or X-frame) and a linear V-groove formed on a movable body (X-frame or Y-frame), for example, which configures a guide portion for defining the moving direction of the movable body in the direction along the both linear V-grooves and guiding the movable body in the same direction. An ultrasonic actuator which generates elliptical vibration on a surface thereof is disposed on the sliding plate side of the movable body in the guide portion in a pressed manner. The movable body is driven in the rotational direction of the elliptical vibration generated by driving the ultrasonic actuator.
The guide portion is arranged on a region closer to one end of the movable body itself, and the ultrasonic actuator is arranged, pressed against the movable body side of the guide portion. In this case, the pressing force of the ultrasonic actuator is applied to the fixed body (frame or X-frame) through the movable body in a direction perpendicular to an axis line connecting the centers of the rolling bodies of the guide portion.
Accordingly, in order to secure a balance of the pressing state with respect to the movable body itself, an elastic member such as a spring, which applies a biasing force in a direction perpendicular to the axis line connecting the centers of the rolling bodies of the guide portion, is arranged on the region closer to the other end of the movable body.